The crew tied to the dock at D.F.C. International, a Commercial Street tuna dealer, pulled a tarp off its haul and hooked it to the winch. A 73-inch bluefin tuna, estimated at 300 pounds, emerged from the crushed ice, rose about 15 feet to the warehouse and was pulled onto a pallet for dressing.
These landings have been getting rarer for years as the bluefin tuna catch has declined in the United States. Those that are brought in tend to be thinner and of lower quality, according to a recent study released from the University of New Hampshire and fishermen's anecdotes.
The study suggests several reasons, which many tuna fishermen agree with, that could be responsible for or could be combining to create the decline, including tougher competition from trawlers and from marine predators for food in New England waters, changes in spawning grounds because of ocean temperature and current changes, and overfishing in the eastern Atlantic Ocean and the Mediterranean Sea that is sending some bluefin to the west.
"We always caught the quota until 1995," said Mark Godfried, a retired Gloucester tuna fisherman and dealer, who is now a consultant for fishing businesses.
Godfried and other fishermen believe the introduction of midwater trawlers, large vessels that pull cone-shaped nets behind them to catch herring, mackerel and other pelagics, that year is at least part of the reason bluefin tuna have declined. Tuna, along with many other sea creatures, feed off herring and mackerel.
Tuna fishermen have been pushing for midwater trawling bans for years and recently succeeded in obtaining a summertime ban in a parcel of ocean stretching from Cape Cod Bay to the Canadian border known as Area 1A. Canada has an outright ban on midwater trawling, but does allow one research trawler.
Now dealers and fishermen believe there are more tuna locally this year. Daniel Bubb, owner of D.F.C. International, said vessels landed seven or eight tuna on his dock last week. However, the number of dogfish, which are small predatory sharks, eating bait are making them difficult to catch.
Bubb said the ban has helped bring tuna closer to shore, but the dogfish eat the bait before a tuna can get there.
"If we could get through the dogfish, they could catch plenty of tuna," he said.
The National Marine Fisheries Service banned the harvest of dogfish, saying the species' females need to be protected to rebuild its population. Massachusetts recently lifted its ban, which covers state waters from the high tide line to three miles out, citing reports by fishermen over the last several years of an explosion in the number of dogfish.
"Dogfish prey on mackerel, on herring, codfish, haddock, they prey on everything," said Bubb. The National Marine Fisheries Service "isn't opening them for landing."
Bluefin being caught now through the end of next month are supposed to be the fattest and most valuable, but the UNH study concluded, using catch data from the Yankee Fishermen's Cooperative in Seabrook, N.H., that the likelihood of catching a top-grade bluefin in September slid from 60 percent in 1991 to about 20 percent in 2004.
However, the probability of catching one of lower quality, meaning they have less fat and oil, in September jumped from 15 percent in 1991 to almost 80 percent in 2004.
"We've had a real influx of small fish around," Bubb said. "At Stellwagen Bank this year there has been a tremendous amount of small fish for the months of June and July. Any day you could have gone to Stellwagen and caught 50 to 60 inches."
The minimum length of a bluefin tuna commercially landed is 73 inches, which takes a bluefin about seven years to achieve.
Recent studies have also found more tuna are migrating west across the Atlantic than previously thought. The UNH study noted that tuna swimming such long distances are bound to be leaner when caught.
"About 35 percent of the tuna population crosses the ocean," Godfried said.
The UNH study's authors found "highly significant declines in the fat and oil content and shape of northern bluefin tuna landed in the Gulf of Maine over the last 14 years, corroborating the observations of fishermen. Northern bluefin tuna arrive in leaner condition and are not increasing their fat stores on the feeding grounds as they did in the early 1990s. This was particularly true in late summer and early fall, when fish usually fatten and become more rotund."
Thinner tuna can result from one, or the combination, of several occurrences. Godfried noted an area in the Gulf of Mexico that tuna use for spawning is lower in oxygen and does not have the life it previously supported.
Spawning in different locations would likely change historic data and patterns, the UNH study noted.
Changes in ocean temperature and currents are also shifting fish northward, Godfried, White and Bubb agreed.
"Over the last five or six years, there's been a shift in pelagic migration patterns 300 to 400 miles north," Godfried said. "The larger fish are in Canada, the smaller fish previously seen off the coast of the Delmarva Peninsula and New Jersey are now up here."
Canada has met its quota continuously while the United States has not. In fact, Americans have traded a portion of their 1,391.2 ton quota to Canada and Mexico because they have not met it.
"The fish are still there, they just go up to Canada," said John White, owner of Fisherman's Outfitters on Main Street and a former president of the North Shore Community Tuna Association.
Finding bluefin is an expensive undertaking and many boats also may be waiting until more fishermen bring tuna back to be more sure of their investment.
"It's also a lack of effort," said Godfried. "Few are willing to spend money in bait and fuel. People think this might be a good season, but a lot of guys have sold their gear after 10 years of bad landings."